RUSSIAN ACADEMY OF SCIENCES PROGRAM SYSTEMS INSTITUTE

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RUSSIAN ACADEMY OF SCIENCESPROGRAM SYSTEMS
INSTITUTE
SYSTEM ANALYSIS RESEARCH CENTER
Head Professor A.M.Tsirlin, Doctor of Sciences

• Optimal Control of Temperature Fields for Cooling
  of Supercomputer Facilities and Clusters and
  Energy Saving for Supercomputer Centers

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Importance of the Investigation

• More than 40 of overall energy produced is used
  to maintain temperature fields (e.g. heating,
  air-conditioning, thermostatting of buildings,
  cryogenic systems, etc.) including 8 of energy
  expenses for ventilation.

System Analysis Research Center of PSI RAS
investigates a problem of thermostatting leading
to maintain temperature fields of pregiven
configuration using minimal energy input. A
partial case of this problem is a problem on
rational cooling of a supercomputer. An essential
part of energy consumed by the supercomputer is
spent for cooling.
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Existing Cooling System Shortcomings

1. The air for cooling is taken from the room where
   the super-computer is located. This air is
   previously warmed up (especially in winter).
   Thus, we spend energy to warm the cooling air,
   and consequently to reduce the efficiency of
   cooling. The return of the warm air to the room
   requires an additional air-conditioning.
2. The installation of the supercomputer does not
   take into account hydrodynamic characteristics of
   air flows. Cables increment hydraulic resistance,
   which influences on the energy expenses.
3. Coolers themselves produce heat while working
   therefore the energy input increases.
4. Reliability of the system is low because failure
   of a cooler implies failure of the correspondent
   computer unit.
5. Heat exchange process is thermodynamically
   imperfect. To increase the efficiency of the
   process it is necessary to maintain ratio of
   temperatures of cold and hot agents to be
   constant.

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Existing Cooling System Shortcomings
Dependencies of temperature of cooling agent
Tcold is represented in the diagrams with respect
to length of a printed circuit board and
temperatures of chips located on the board.
Output temperature of the cooling agent is higher
for the case when
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Existing Cooling System Examples
Air removal unit APC
zBox supercomputer, Zürich
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Existing Cooling System Examples
Air cooled router cabinet, Cray
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Enhanced Cooling System Features

• Optimal control of temperature and flow intensity
  of cooling air subject to temperature of outside
  air will allow minimization of the energy
  expenses.
• Excess pressure in the cluster box and removal of
  warmed air outwards.
• Optimal allocation of chips on computer units and
  installation of cables will take into account
  hydrodynamic characteristics of air flows.
• Central control unit for preparation and feeding
  of cold air can be doubled. That is why
  reliability of the system can be increased.
• Unification of cooling systems will allow the
  possibility to use it with clusters of arbitrary
  configuration.

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Enhanced Cooling System Features
Dependency of the air humidity ? with respect to
indoor temperature T is shown in the picture for
three different values of outdoor
temperature10oC, 5oC, 0oC. It is shown that
water condensation on the computer units is
impossible, even if humidity of the input air is
very high.
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Problems to be Solved

• To determine configuration of temperature field
  of cooling fluids corresponding to minimal energy
  expenses. To develop a system of cooling
  maintaining this optimal field.
• To determine an optimal intensity and temperature
  of air input flow with respect to outdoor
  temperature.
• To develop rational outlines for installation of
  circuit boards and their allocation in the box.
• To estimate the advisability of introducing an
  additional loop with natural circulation of
  cooling fluid.